One known rotation transmission device which can selectively transmit rotation of a driving shaft to a driven shaft includes a two-way clutch and an electromagnetic clutch for selectively engaging and disengaging the two-way clutch.
The rotation transmission device disclosed in Japanese Patent Publication 2009-293679A includes an outer ring, an inner ring mounted inside the outer ring, and a control retainer member and a rotary retainer member each having bars and mounted between the inner and outer rings such that the bars of the control retainer member are arranged circumferentially alternating with the bars of the rotary retainer member, whereby pockets are defined between circumferentially adjacent pairs of the bars of the respective retainer members. The rotation transmission device further includes rollers each two of which are mounted in one of the pockets, and elastic members each mounted in one of the pockets and biasing the two rollers in the one of the pockets away from each other to a stand-by position where the rollers can instantly engage a cylindrical surface formed on the inner periphery of the outer ring and one of cam surfaces formed on the outer periphery of the inner ring such that when the inner ring rotates in either direction, one of each pair of rollers engages the cylindrical surface and the cam surface, thereby transmitting rotation of the inner ring to the outer ring.
The rotation transmission device further includes an electromagnetic clutch mounted on an input shaft connected to the inner ring. The electromagnetic clutch is configured to move the control retainer member in the axial direction. When the control retainer member is moved in the axial direction by the electromagnetic clutch, the retainer members are rotated relative to each other in the direction in which the circumferential widths of the pockets decrease due to the action of a torque cam provided between the opposed surfaces of a flange of the control retainer member and a flange of the rotary retainer member, thereby moving the pairs of rollers in the respective pockets to the disengaged position and thus preventing transmission of rotation from the inner ring to the outer ring.
In this rotation transmission device, when the control retainer member is moved by the electromagnetic clutch in the direction in which the flange of the control retainer member moves away from the flange of the rotary retainer member, the control retainer member and the rotary retainer member are rotated relative to each other in the direction in which the circumferential widths of the pockets increase under the biasing force of the elastic members mounted between the respective pairs of rollers. Thus the rollers can instantly engage the cylindrical surface and the cam surfaces, so that the rollers scarcely move in the circumferential direction when engaging the cylindrical surface and the cam surfaces, and the response time is short too.
In the rotation transmission device disclosed in Japanese Patent Publication 2009-293679A, the two-way clutch constituted by the inner and outer rings, the pairs of rollers and the retainer members, and the electromagnetic clutch for controlling the two-way clutch are covered by a housing. With the two-way clutch and the electromagnetic clutch mounted in position in the housing, if the two-way clutch and the electromagnetic clutch are movable relative to each other or relative to any other members of the device, it is impossible to control the two-way clutch with high accuracy.
In order to avoid this problem, it has been an ordinary practice to insert a shim between the opposed portions of the built-in components comprising the two-way clutch and the electromagnetic clutch to keep these components immovable. But in order to reliably keep the built-in components immovable, it is necessary to insert shims having different thicknesses one by one to select the most suitable one. This step is extremely troublesome. The shim increases the number of parts and thus the cost, of the rotation transmission device. It is therefore desired to assemble the rotation transmission device more easily and to reduce the cost.